The long range goal is to understand the mechanism of protein-mediated transport across biological membranes, and to apply this knowledge to advance our understanding of integrated physiological processes in which ion transport is intimately involved. Regulation of the heart beat and kidney function are among the potential applications, and serve to relate this work to health problems in these areas. The immediate specific aims are to resolve existing experimental ambiguities in the biochemical reaction cycle for the ATP-driven Ca pump of sarcoplasmic reticulum, and to update current ideas about the mechanism of this particular transport system. The studies to be carried out to accomplish this include measurement of the number of Ca binding sites per polypeptide chain of the protein, the number of functionally important conformational states through which the protein must pass in each reaction cycle, and evaluation of thermodynamic parameters for ion binding and conformational transitions. Some of these studies will be repeated using ATP-driven Na, K pump protein. This system is believed to have a transport mechanism similar to that of the sarcoplasmic reticulum Ca pump.